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H T Lee

Publications and source records attributed to H T Lee.

At least 73 records · Page 4Linked to original sources
PubMed1994

Effect of superoxide dismutase on the development of preimplantation mouse embryos.

The role of superoxide dismutase (SOD) was tested on preimplantation development of mouse embryos in vitro. The presence of SOD in ovarian antral follicles and in oviductal and uterine secretions was also investigated. Zygotes from superovulated ICR female mice were cultured in modified Whittingham's T6 medium supplemented with SOD (0 to 370 U) or EDTA (100 muM) at 37 degrees C under 5% CO(2) in air. Supplementation of SOD (370 U) significantly promoted the development of zygotes to the blastocyst stage (45%) as compared to that of the controls (1.4%). This favorable effect of SOD was comparable to that of EDTA and completely suppressed by anti-SOD antibody. Blastocysts cultured with SOD consisted of 78.2+/-10.4 blastomeres and possessed as many blastomeres as those (81.6+/-9.3) developing in vivo; blastocysts cultured with EDTA had significantly fewer blastomeres (42.6+/-13.7). These findings suggest that SOD protects embryos against oxidative insults and that it can be an effective substitute for EDTA for supporting mouse embryo development in vitro. The SOD activity was detected in 3 different lumina from mouse reproductive organs, and SOD was identified as a cytosolic Cu,Zn-SOD on photochemically stained polyacrylamide gels. Our results suggest that oxidative injury may be responsible for developmental retardation of preimplantation-stage mouse embryos in vitro and that Cu,Zn-SOD may play a crucial role in protecting embryos against oxygen toxicity in vivo as well as in vitro.

Journal Article↗
PubMed1993

Differential sensitization of cardiac actions of adenosine in rats after chronic theophylline treatment.

To determine the effect of chronic adenosine receptor blockade on atrial responsiveness, we administered theophylline to rats in their drinking water (0.6 mg/ml) for 2 wk. Inotropic and chronotropic responses to the adenosine receptor agonists N6-cyclopentyladenosine (CPA) and 5'-(N-ethylcarboxamido)-adenosine (NECA) were then measured in isolated atria from treated and control animals. The indirect (antiadrenergic) actions of CPA and NECA on force and rate, measured during beta-adrenergic receptor stimulation by isoproterenol, were markedly sensitized (2- to 10-fold reductions in the agonist concentration needed to obtain a half-maximal response) after theophylline. The sensitization was homologous because inotropic and chronotropic responses to carbachol were not affected by theophylline. The direct negative inotropic and chronotropic actions of CPA and NECA, measured without concomitant beta-adrenergic stimulation, were not sensitized after theophylline. The number of atrial A1-receptors, measured by antagonist radioligand binding (maximum specific binding at saturation), was increased by 22% in theophylline-treated rats [66.2 +/- 3.4 vs. 54.3 +/- 1.9 (control) fmol/mg protein, P < 0.05]. Competition binding indicated that the fraction of coupled (high-affinity) receptors was unchanged. The number of ventricular A1-receptors was increased to a similar extent without any change in coupling. Thus chronic dietary theophylline upregulated cardiac A1-adenosine receptors without changing coupling state or affinity and sensitized rat atria to the indirect, antiadrenergic, inhibitory inotropic and chronotropic actions of adenosine receptor agonists.

Adenosine↗
PubMed1993

Cardiac desensitization to adenosine analogues after prolonged R-PIA infusion in vivo.

To determine the effects of chronic in vivo stimulation of adenosine receptors, R-(-)-N6-(2-phenylisopropyl)adenosine (R-PIA), a selective A1 receptor agonist, was administered to rats as a continuous 7-day infusion (200 nmol/h). Inotropic and chronotropic responses of isolated atria to adenosine receptor agonists were markedly desensitized compared with the responses of atria from age-matched control animals. Carbachol's negative chronotropic effect was also attenuated, indicating a heterologous mode of desensitization. Antagonist radioligand binding assays indicated a 52% reduction in A1 adenosine receptor maximum binding, and competition binding assays revealed a significant loss of G protein-coupled high-affinity A1 receptors in atria from R-PIA-treated rats. Inhibitory G proteins (Gi) were significantly reduced, as quantified by immunoblot analysis, with no change in the amount of stimulatory G proteins. Ventricular membranes from R-PIA rats showed loss of Gi and uncoupling of A1 receptors, without a significant change in A1 receptor density. Thus chronic R-PIA infusion desensitized rat atrial muscle to the effects of adenosine receptor agonists via several regulatory adaptations, including downregulation of A1 adenosine receptors, uncoupling of A1 receptors from their associated G proteins, and loss of Gi proteins.

2-Chloroadenosine↗
PubMed1992

Regulation of alpha-amylase-encoding gene expression in germinating seeds and cultured cells of rice.

Four alpha-amylase-encoding cDNA (alpha Amy-C) clones were isolated from a cDNA library derived from poly(A)+RNA of gibberellic acid (GA3)-treated rice aleurone layers. Nucleotide sequence analysis indicates that the four cDNAs were derived from different alpha Amy genes. Expression of the individual alpha Amy gene in germinating seeds and cultured suspension cells of rice was studied using gene-specific probes. In germinating seeds, expression of the alpha Amy genes is positively regulated by GA3 in a temporally coordinated but quantitatively distinct manner. In cultured suspension cells, in contrast, expression of the alpha Amy genes is negatively and differentially regulated by sugars present in the medium. In addition, one strong and one weak carbohydrate-starvation-responsive alpha Amy genes have been identified. Interactions between the promoter region (HS501) of a rice alpha Amy gene and GA3-inducible DNA binding proteins in rice aleurone cells were also studied. A DNA mobility-shift assay showed that the aleurone proteins interact with two specific DNA fragments within HS501. One fragment is located between nt -131 to -170 and contains two imperfect directly repeated pyrimidine elements and a putative GA3-response element. The other fragment is located between nt -92 to -130 that contains a putative enhancer sequence. The interactions between aleurone proteins and these two fragments are sequence-specific and GA-responsive.

Base Sequence↗
PubMed1992

Differential expression of Hz-1 baculovirus genes during productive and persistent viral infections.

Hz-1 viral RNA transcription was studied during productive and persistent infections. The RNAs were localized to 10- to 30-kb regions within the viral genome, and the timing of their expression was determined. During productive infections, we detected 101 virus-specific transcripts that could be grouped into three categories by time of appearance. At 2 h postinoculation (p.i.), a total of 34 virus-specific transcripts were detected. An additional 51 and 16 virus-specific transcripts appeared between 4 and 6 h p.i. and at 8 h p.i., respectively. After 8 h, no new transcripts were found. Under conditions of persistent infection, we detected only one viral persistency-associated transcript (PAT1). The region of the viral DNA which encodes PAT1 was cloned. During productive infections, three transcripts were derived from this region. Each had the same polarity as PAT1. One of them was of the same size as PAT1 and had similar, if not identical, 3' and 5' ends. This report provides detailed and very useful information concerning sequentially expressed transcripts of the Hz-1 baculovirus.

Animals↗
PubMed1990

Neuronal mapping of the heart with 6-[18F]fluorometaraminol.

The false neurotransmitter metaraminol labeled with fluorine-18 has been used to noninvasively assess regional adrenergic nerve density in the canine heart. Intravenous administration of 6-[18F]fluorometaraminol (FMR) results in high, selective accumulation of radioactivity in the heart; drug blocking studies with desipramine and reserpine confirm the neuronal locus of FMR. Iodine-125 labeled metaraminol, however, shows no selective accumulation in the canine heart. Positron emission tomography (PET) analyses with FMR of closed-chest dogs bearing left ventricular neuronal defects clearly delineate the region of neuronal impairment; blood perfusion in the left ventricle wall was homogeneous as determined by [13N]NH3 tomograms. The accumulation of FMR in regionally denervated dog heart correlates closely (r = 0.88) with endogenous norepinephrine concentrations. PET-generated 18F time-activity curves demonstrate marked kinetic differences between normal and denervated myocardium. FMR/PET analysis could be used to assess the heterogeneity of sympathetic innervation in human heart disease contingent on the development of FMR with sufficiently high specific activity to clearly avoid pressor activity.

Animals↗
PubMed1990

Inhibition of the activities of P450 cholesterol side-chain cleavage and 3 beta-hydroxysteroid dehydrogenase and the amount of P450 cholesterol side-chain cleavage by testosterone and estradiol-17 beta in hen granulosa cells.

We have found that androgens and estradiol-17 beta (E2) produced by theca cells suppress progesterone (P4) secretion by granulosa cells of the domestic hen in a dose-dependent manner. Furthermore, testosterone (T) and E2 inhibited the conversion of cholesterol to pregnenolone (P5) and of P5 to P4, respectively. The aim of this study was to determine if T and E2 suppress P4 biosynthesis by changing activities of the cytochrome P450 cholesterol side chain cleavage (P450scc) and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) (Exp I) and the amount of P450scc (Exp II). Granulosa layers of the largest follicle of two to four hens were obtained 22 h before ovulation, pooled, and isolated granulosa cells were prepared. In Exp I, the specific activities of the P450scc and 3 beta-HSD were measured in mitochondrial and microsomal proteins of granulosa cells, respectively, in the presence of T or E2 (0-10 microM). Addition of T to mitochondrial proteins increased the Michaelis-Menten constant (Km) with no change in the maximum velocity (Vmax) of the P450scc, which suggests competitive inhibition (Ki = 30.9 microM), whereas E2 had no effect on Km and Vmax of the P450scc. Likewise, addition of E2 to microsomal proteins increased the Km with no change in the Vmax of the 3 beta-HSD, which suggests competitive inhibition (Ki = 15.1 microM), whereas T had no effect on Km and Vmax of the 3 beta-HSD. In Exp II, granulosa cells (3 x 10(5)/3 ml.tube) were incubated for 0-12 h in triplicate for each combined treatments of 25-OH-cholesterol (8 microM) and cyanoketone (10 microM), T, or E2 (0-10 microM) in the presence or absence of LH (25 ng). Protein content and P5 secretion were measured and the amount of P450scc was determined by Western blot analysis. Incubation of granulosa cells with T decreased the amount of the P450scc in granulosa cells cultured for 12 h and P5 secretion in granulosa cells cultured for 3 h or longer (P less than 0.05), without a change in protein content and cell viability. Our results suggest that P4 production by granulosa cells is suppressed by T and E2 acting as competitive inhibitors of the P450scc and 3 beta-HSD, respectively, and by T decreasing the amount of the P450scc. We conclude that steroidogenesis in the follicle of the chicken is regulated through the interaction of theca and granulosa layers.

3-Hydroxysteroid Dehydrogenases↗
PubMed1989

Inhibitory sites of androgens and estradiol in progesterone biosynthesis in granulosa cells of the domestic hen.

In a previous in vitro study we found that androgens and estradiol (E2) suppress progesterone (P4) production by the granulosa cells isolated from the largest follicle of the domestic hen in a dose-dependent manner. The presence of an aromatase inhibitor did not block the inhibitory action of androgens. The addition of androgen plus E2 to the granulosa cells had an additive effect on suppressing P4 secretion. The aim of this study was to determine the loci in the steroid biosynthetic pathway where androgens and E2 inhibit P4 production by the granulosa cells. Granulosa layers of the largest follicles removed from two or three hens 22 h before ovulation were pooled. Dispersed granulosa cells were incubated for 3 h in triplicate for each treatment, and pregnenolone (P5) and P4 secretion were measured in medium and cells. Experiments were replicated three or four times. Treatment of granulosa cells with cyanoketone (0-100 microM), an inhibitor of 3 beta-hydroxysteroid dehydrogenase, increased P5 production and decreased P4 production in a dose-dependent manner, with maximal production of P5 and suppression of P4 production at 10 microM cyanoketone. The addition of 25-hydroxycholesterol (25OHCh) or P5 (0-16 microM) caused a dose-related increase in basal and LH-stimulated steroid production. The maximal production of P5 or P4 was found at 8 microM 25OHCh or P5. Also, the effect of LH (0-100 ng) on granulosa cell steroidogenesis was examined with or without 8 microM 25OHCh or P5. The half-maximal and maximal doses for P5 or P4 production were 5 and 25 ng LH, respectively. Next, suppression of P5 production by androstenedione, testosterone, dihydrotestosterone, and E2 (each at 0-10 microM) was tested in the presence of 25OHCh plus cyanoketone with or without LH. We found a dose-dependent suppression of P5 production by androgens (1-10 microM), but not by E2. However, when we added the above steroids to granulosa cells in the presence of P5 with or without LH, only E2 (1 and 10 microM) caused a significant suppression of P4 production. Our results suggest that 1) androgens primarily act at the conversion site of cholesterol to P5 to suppress P4 production; and 2) E2 acts at the conversion site of P5 to P4 to suppress P4 production. We conclude that production of androgens and E2 by thecal cells may regulate P4 biosynthesis by granulosa cells in the domestic hen.

Androgens↗
PubMed1988

Inhibition of progesterone secretion from granulosa cells by estradiol and androgens in the domestic hen.

We previously reported no difference in progesterone (P4) secretion from the granulosa layer of the largest follicle (F1) of the domestic hen regardless of the maturity of the F1 follicle. However, coincubation of the granulosa and thecal layers resulted in inhibition of P4 secretion from the less mature F1, but not from the more mature F1. The goal of this study was to determine if estradiol (E2) and androgens secreted by the thecal layer suppress P4 production by the granulosa cells. We removed the granulosa layer from less mature F1 follicles and dispersed granulosa cells (1 x 10(5)) were incubated (3 h) in triplicate with one of these treatments: control, E2, testosterone (T), androstenedione (A), and dihydrotestosterone (DHT; at concentrations of 1 x 10(-7), 1 x 10(-6), and 1 x 10(-5) M), LH (100 ng) as well as LH plus E2, T, A, and DHT at the same concentrations. P4 secretion was measured in the medium and cells, and the experiment was replicated seven times. We found a dose-related suppression of basal and LH-stimulated P4 production by all steroids. In a second experiment (n = 3-5), we tested the specificity of the androgens in suppressing P4 production by granulosa cells by using the aromatase inhibitor 7-(4'-amino)phenylthio-4-androstene-3,17-dione. This compound did not reduce the effectiveness of T in suppressing P4 production. Finally in Exp 3 (n = 4-7), E2 and T were tested individually and in combination at concentrations of 1 X 10(-8)-1 X 10(-5) M. We found a possible synergistic effect, in that the combination of E2 plus T suppressed P4 to a greater degree than either steroid alone. Our results indicate that 1) E2 and androgens suppress basal and LH-stimulated P4 production by granulosa cells in a dose-related manner; 2) androgen suppression of P4 production is not mediated by aromatization to estrogen; and 3) the suppressive effects of E2 and androgens may be synergistic. We conclude that E2 and androgens secreted by the thecal layer may regulate P4 production by the granulosa layer.

Androgens↗
PubMed1986

Iodine-123-4-amino-3-iodobenzylguanidine, a new sympathoadrenal imaging agent: comparison with iodine-123 metaiodobenzylguanidine.

Iodine-123-4-amino-3-iodobenzylguanidine ([123I]AIBG), an analog of 123I metaiodobenzylguanidine ([123I]MIBG), has an advantage in having a more rapid and simple synthesis. This, combined with animal data that suggested a greater affinity of the new radiopharmaceutical for the autonomic innervation of the myocardium led us to study the biodistribution of [123I]AIBG in three men with metastatic pheochromocytoma. In all instances, [123I]AIBG revealed the same metastatic deposits shown by [123I]MIBG. Iodine-123 AIBG uptake, however, was greater than [123I]MIBG in lung, gut, and spleen. These higher backgrounds may pose diagnostic problems in some cases.

3-Iodobenzylguanidine↗
PubMed1982

Characterization of a ColE1-like plasmid isolated from Shigella sonnei.

A multicopy plasmid, 4.7 kb in size, was isolated from Shigella sonnei and named pKY1. This plasmid produces a colicin E1-like bacteriocin (colicin E1*) in E. coli cells. The cells harboring pKY1 are immune not only to this bacteriocin but also to colicin E1, and the cells harboring Co1E1 show immunity to colicin E1* as well. Although these two plasmid DNAs have different cleavage maps and are compatible with each other, pKY1 shows partial DNA homology with ColE1 DNA. In this paper, we report the isolation and properties of several Tn3 inserted pKY1 mutants, and propose a preliminary genetic map of pKY1. It was also found that this plasmid is not capable of self-transmission and is poorly mobilized by the F factor.

Chromosome Mapping↗
PubMed1981

Selective renal artery embolization for control of biopsy-induced bleeding.

Two cases of selective renal artery embolization for control of bleeding induced by arteriovenous malformation are described. Both cases occurred after percutaneous renal biopsy and involved massive hematuria, unresponsive to conservative treatment. Arteriography in both cases demonstrated an arteriovenous fistula in the area of the biopsy, and selective embolization with an artificial clot resulted in prompt cessation of bleeding. In one case, follow-up angiograms showed a minimal anatomic defect, and renal function studies were unchanged. Selective renal artery embolization is an acceptable method for correcting bleeding due to biopsy-induced arteriovenous malformation.

Adult↗
PubMed1981

Primary necrotizing arteritis of the main renal artery presenting as accelerated renovascular hypertension.

Presented is a unique case of accelerated hypertension in a 26-year-old black man. Clinically, the patient was found to have a left renal artery lesion and lateralizing renal vein renins. At surgery, a stenosing lesion was found in the artery supplying the upper pole of the left kidney. This was caused by a densely fibrotic mass involving the main renal artery. Microscopy revealed a necrotizing arteritis with no other arteries involved. This case of primary necrotizing arteritis of the main renal artery appears to represent a new entity because of its pathological and clinical differences with the known forms of large vessel arteritis. It is possible that this may represent a particularly acute and necrotizing stage of Takayasu's aortitis, or an extremely rare case of classical periarteritis nodosa confined solely to the main renal artery. The renin tissue assays document the hyperreninemia produced by arterial stenosis. The differential diagnosis of the lesion is considered, and the pathophysiology of hypertension due to large vessel arteritis is discussed.

Adult↗